Why did my market order in the pre-open session become a limit order?

The pre-open session is for a duration of 15 minutes from 9:00 am to 9:15 am.

It is broken down into two sub-sessions:

1. Order Collection Period:

The order collection period of 8* minutes shall be provided for order entry, modification and cancellation. (* - System driven random closure between 7th and 8th minute). During this period orders can be entered, modified and canceled.

2. Order Matching Period:

Order matching period starts immediately after completion of order collection period. Orders are matched at a single (equilibrium) price which will be open price. The order matching happens in the following sequence:

• Eligible limit orders are matched with eligible limit orders

• Residual eligible limit orders are matched with market orders

• Market orders are matched with market orders

All outstanding unmatched orders, after order matching period, are moved to the normal market retaining the original time stamp.

Limit orders are sent at the limit price and market orders are sent as limit orders at the discovered equilibrium price. In a situation where no equilibrium price is discovered in the pre-open session, all market orders are moved to normal market at previous day’s close price or adjusted close price / base price following price time priority.

Click here to know more about the pre-open session.